Camshaft phasing mechanisms allow selective adjustment of valve timing for internal combustion engines by selectively advancing or retarding the positions at least some of the lobes on a camshaft, thereby allowing associated valve movements to occur either earlier or later in the gas exchange cycle. For example, engines may operate more efficiently or effectively during one set of operating conditions when the valve timing is advanced, i.e., such that a valve(s) movement occurs earlier during the combustion cycle. Additionally, it may be desirable during a second set of operating conditions to retard the valve timing, i.e., such that a valve(s) movement occurs later during the gas exchange cycle. Adjusting the relative positions of at least some of the lobes on a camshaft allows internal combustion engines to operate with improved fuel economy, torque, and emissions.
Lobes of a camshaft may be used to open and close valves or to actuate pushrods which in turn open and close valves of an engine. While cam phasing mechanisms are useful, they may still suffer from inherent limitations of mechanical valve actuation systems. For example, lift and duration of a valve may be generally incapable of being adjusted during engine operation. As a result, valve opening and/or closing parameters of an engine may not be ideal across all engine operating conditions.
Accordingly, there is a need for a camshaft assembly that addresses the above problems.